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SubjectRe: [linux-usb-devel] usb still sucks battery in -rc7-mm1
On Sun, 24 Sep 2006, Pavel Machek wrote:

> I made some quick experiments, and usb still eats 4W of battery
> power. (With whole machine eating 9W, that's kind of a big deal)...
> This particular machine has usb bluetooth, but it can be disabled by
> firmware, and appears unplugged. (I did that). It also has fingerprint
> scanner, that can't be disabled, but that does not have driver (only
> driven by useland, and was unused in this experiment).
> Any ideas?

(I have not followed the thread, so bear with me if I say anything

I have encountered at least 3 hubs (2 usb2 & 1 usb1) that will consume a
lot of power (about 2-2.5W if the laptop power consumption readings are to
be trusted) and heat up a lot (to the point of being too hot to touch for
more than a few seconds) even when no devices are connected, at least on
Linux. I have not tested them on a Windows machine to see if this is the
case there. The USB2 ones used Cypress chips. I do not know what your h/w
config is, but perhaps this is a similar case ?


Theodoros Kalamatianos

PS: Note that the 2-2.5W consumption is the maximum that the laptop USB
port can provide, and I have noticed that with the hub's external power
supply connected it heats up even more.
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